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SubjectRe: [RFC PATCH] x86: stop machine text poke should issue sync core
(2011/03/03 15:10), H. Peter Anvin wrote:
> On 02/28/2011 07:24 AM, Mathieu Desnoyers wrote:
>>
>> Index: linux-2.6-lttng/arch/x86/kernel/alternative.c
>> ===================================================================
>> --- linux-2.6-lttng.orig/arch/x86/kernel/alternative.c
>> +++ linux-2.6-lttng/arch/x86/kernel/alternative.c
>> @@ -612,6 +612,12 @@ static int __kprobes stop_machine_text_p
>>
>> flush_icache_range((unsigned long)tpp->addr,
>> (unsigned long)tpp->addr + tpp->len);
>> + /*
>> + * Intel Archiecture Software Developer's Manual section 7.1.3 specifies
>> + * that a core serializing instruction such as "cpuid" should be
>> + * executed on _each_ core before the new instruction is made visible.
>> + */
>> + sync_core();
>> return 0;
>> }
>>
>
> Isn't this executed from an IPI handler, which will return with IRET (a
> serializing instruction) anyway?

No, now stop_machine uses per-cpu workqueue, so that handler will be
executed from worker threads. There is no iret anymore.

BTW, Mathieu, since the latest kernel has batch-text_poke_smp, this patch
needs to be updated.

Thank you,

--
Masami HIRAMATSU
2nd Dept. Linux Technology Center
Hitachi, Ltd., Systems Development Laboratory
E-mail: masami.hiramatsu.pt@hitachi.com


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